Reply to Mr. Farey's Geological Observations. 47 



which terminate upon the red marie on the southern sidej 

 but there are no indications of the surface having been 

 fractured along the line where the termination of th'e sand 

 rock 18 observed. I therefore repeat again my request, that 

 Mr. Farey would distinctly point out'the situations where 

 this greal fault, on which he has written so much, can be 

 seen and proved to exist. A particular fracture at any one 

 part, will not be sufficient to prove the identity of a fault 

 m any other part, without further evidence than the con- 

 jectures of the observer. 



The assumption of imaginary facts in geology has a ten- 

 dency to retard the progress of the science more than any 

 other cause. The application of conjectures to explain the 

 operation of causes which we have not been able to prove or 

 trace, may be allowed where such conjectures are kept di- 

 stinct from facts : but when they are confounded with 

 them, and reasoned upon with as much solemn gravity as 

 if they were real entities, they "darken council W words 

 without knowledo-e." 



At the conclusion of Mr. Farey's letter, he attributes to 

 me the adoption of Mr. VVhitehurst's opinion that the 

 toad-stone of Derbyshire has been injected in a slate of 

 fusion between the beds of limestone. This opinion 1 have 

 most distinctly disavowed ; though I am inclined to believe 

 that the basaltic amygdaloid of that county has been the 

 product of submarine volcanoes thrown over the lime at 

 different periods of time when the whole of that country 

 was under the surface of the ocean. This was offered 

 merely as a conjecture, to which no importance was at- 

 tached. 



I am, sir. 



Your obedient servant, 



July 14, 181'i. T. o 



„ c ,. • • , , ^^- Bakevvell. 



1 .b.— It IS with some reluctance that I have been com- 

 pelled to enter the lists of controversy with Mr. Farey but 

 a.s I am at this time examinintj for the Earl ofMoira a part 

 of Charnwood Forest, I ukfc the opportunity of observ-incr 

 that Mr. Farey's siaiement, that there is no appearance of 

 stratification m the slate rocks of this district, is erroneous. 

 All these rocks which f have examined are composed of 

 grau wacce, roof -late, horn-stone slate,, and porphyritic 

 slate, which are most distincily stratified, but in an op- 

 posite direction to the slatv cleavage of the stone On the 

 mincra'ogy of this district I shall probably offer some re- 

 iriaiks to the public. 



X[. Dr. 



